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Title: Divergence in drought‐response traits between sympatric species of Mimulus
Abstract

Differential adaptation to local environmental conditions is thought to be an important driver of speciation. Plants, whose sedentary lifestyle necessitates fine‐tuned adaptation to edaphic conditions such as water availability, are often distributed based on these conditions. Populations occupying water‐limited habitats may employ a variety of strategies, involving numerous phenotypes, to prevent and withstand desiccation. In sympatry, two closely relatedMimulusspecies—M. guttatusandM. nasutus—occupy distinct microhabitats that differ in seasonal water availability. In a common garden experiment, we characterized natural variation within and between sympatricM. guttatusandM. nasutusin the ability to successfully set seed under well‐watered and drought conditions. We also measured key phenotypes for drought adaptation, including developmental timing, plant size, flower size, and stomatal density. Consistent with their microhabitat associations in nature,M. nasutusset seed much more successfully thanM. guttatusunder water‐limited conditions. This divergence in reproductive output under drought was due to differences in mortality after the onset of flowering, withM. nasutussurviving at a much higher rate thanM. guttatus. Higher seed set inM. nasutuswas mediated, at least in part, by a plastic increase in the rate of late‐stage development (i.e., fruit maturation), consistent with the ability of this species to inhabit more ephemeral habitats in the field. Our results suggest adaptation to water availability may be an important factor in species maintenance of theseMimulustaxa in sympatry.

 
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PAR ID:
10372607
Author(s) / Creator(s):
 ;  
Publisher / Repository:
Wiley Blackwell (John Wiley & Sons)
Date Published:
Journal Name:
Ecology and Evolution
Volume:
9
Issue:
18
ISSN:
2045-7758
Page Range / eLocation ID:
p. 10291-10304
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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